Geologically speaking, the generalization that we live in a flat place is true and historically important. Chicago's flatness inspired some of the engineering innovations that would, in turn, make the city a global center of innovation.

The flat postglacial geography of the sluggish Chicago River and its adjacent swamps marked the narrow southwestern edge of the Great Lakes watershed, the perfect spot for a canal to connect the Great Lakes to the Mississippi River watershed. The Illinois and Michigan Canal opened in 1848, but the flat landscape complicated the growing city's sanitation, as the river (more or less an open sewer) contaminated the Lake Michigan drinking water. So Chicagoans built things to overcome the negative effects of the flatness: a tunnel beneath the lakebed that stretched two miles out, beyond the polluted area, to bring in clean drinking water; a sewer system constructed at ground level, which then required raising the grade of the streets; and finally the Sanitary and Ship Canal in 1900, which reversed the flow of the river and made our shit Saint Louis's problem. The soft sedimentary soil required early skyscrapers to have "floating foundations"—essentially vast, heavy underground rafts—that made a building's weight sustainable without having to reach the deep bedrock.

Well, we don't need no stinking mountains! Chicagoans built their own: the skyline of the Loop, with subsidiary ranges up and down Lake Shore Drive. Every day hundreds of thousands of people in cars or on trains or bikes converge towards this man-made mountain range, as beautiful in the changing light and weather as any vista in the world.

Still, it must be noted that the city is actually not entirely flat. Look at a topographical map and you'll see that while Chicago is mostly around 600 feet above sea level, peripheral neighborhoods like Beverly and Rogers Park do feature hills, rare outcroppings of underlying bedrock or the remnants of prehistoric beaches.

Chicago also abounds with artificial elevations: bridges, viaducts, and overpasses, an undulating rhythm that punctuates the flatness.

In fact, I'd argue that the general flatness makes Chicagoans more attuned to any rise or fall of elevation, especially when we walk or ride bicycles around town.

I write this as someone who regularly bikes from my home in Rogers Park to my sweetheart's place in south-suburban Evergreen Park. Sure, the 25 miles are mostly flat, but natural features like the river, along with infrastructure like railroads and expressways, create virtual hills. Ride Halsted from Boystown to Bridgeport and you'll need to downshift and pedal harder on the bridge over the river from Hooker to Erie, then again atop the Ohio feeder ramp, down to Grand, up over the Metra tracks, down to Greektown, then one final rise to surmount the Eisenhower and down to UIC. Later, you'll hit the underpass at the 16th Street viaduct and one final rise on the bridge over the South Branch of the river. An Alpine stage of the Tour de France this ain't, but neither is it the utterly horizontal Chicago of myth. And don't get me started on the Kedzie viaduct over the rail yards from 73rd to 77th—that, my friend, is a hill, even if it was built by traffic engineers rather than geologic processes.

So Chicago's flatness is like so many other tales of this city: it's true, except when it isn't. And both the truth and the exceptions make the place more interesting. v